This invention relates generally to a magnetic roller for use in the drafting system of a textile machine, such as a spinning machine, roving machine, drawframe, card machine, or the like.
In drafting fibers on a textile processing machine, such as a spinning machine, a band of fibers is passed between at least two pairs of rollers, the second, downstream, pair of rollers being driven at a faster rate than the first, upstream, pair of rollers such that the band of fibers becomes elongated, or "drafted" between the two pairs of rollers. A typical drafting system may include two pairs of such cooperating rollers or additional pairs of rollers to form successive drafting zones therebetween.
In order to draft the fibers, pressure must be applied between the rollers in each roller pair in a manner sufficient to cause the nip zone at the interface between the roller pair to both grip and propel the fibrous material. Weights, springs, levers, hydraulic, pneumatic or other pressure systems for forcing the rollers towards one another have been used in the past. However, a drawback of such systems is that they require substantial supporting structures to counteract the external weighting applied to the rollers. The supports must be strong enough to prevent undesirable deflection in the rollers being weighted. Also, bearings must be included which can both support the rollers for rotation and withstand the forces delivered by the external weighting.
As an alternative to the external weighting, magnetic weighting can be used. In magnetic weighting, at least one roll of each roller pair is magnetized such that it is attracted to the other roll of the pair, which is constructed of either a ferrous material or a magnetic material. In this system, the magnetic force between the rollers pulls the rollers together and applies sufficient pressure therebetween to grip and propel the fibers being processed. No additional weights, springs, levers, hydraulic or pneumatic systems are required for weighting the rollers. By eliminating the need for such weighting systems, the corresponding roller support structures can be simplified since roller deflection is essentially eliminated. Also, the bearing systems for the rollers will not have to withstand the externally-delivered forces caused by other types of weighting.
In some magnetic roller designs, the magnets are carried internally within the rollers and are contained within cylinders or sleeves. The shells are typically constructed of a non-magnetic material. With such magnetic roller designs, the magnets and corresponding pole members for the magnets are typically rotatably supported on gudgeons or journals.
Further, prior magnetic rollers were limited by the amount of magnetic force which could be delivered, due to the composition of the magnets used. Because of the type of magnets used and the diameter of the magnets required to achieve the necessary attractive force, a shorter, and therefore a more desirable, draft zone was not achievable between adjacent roller pairs. Additionally, prior magnetic rollers were prone to de-magnetization over time and could actually be de-magnetized if the rollers were not inserted and oriented properly with respect to adjacent rollers.
Prior magnetic roller designs include U.S. Pat. No. 3,134,057, issued to Tsunoo, et al, which discloses a magnetic roller having magnetic pieces fitted on pole rings. U.S. Pat. No. 3,150,419, issued to Aurich, discloses magnetic rollers having conventional magnets carried within a roll and housed by a metal sleeve. The magnets are separated by pole pieces, and gudgeons are used for supporting the rollers for rotation. German Patent document No. 1,185,961, discloses a magnetic roller having magnet rings adjacent to one another and iron pole pieces located adjacent to and outboard of the magnet rings. U.S. Pat. No. 3,457,618, issued to O'Neal, discloses a magnetic crush roll for use with a carding machine, the roll including magnetic modules carried on a shaft. U.S. Pat. Nos. 3,364,545 and 3,605,229, also disclose magnetic crush rolls.
U.S. Pat. No. 4,829,277, issued to Stahura, et al, and U.S. Pat. No. 5,055,812, issued to Abele, et al, both disclose magnetic resonance imaging devices used in the medical field. Each of the patents disclose the use of rare earth magnets of neodymium, iron, and boron alloy compositions.
While prior magnetic roller designs are available, they present limitations which may prevent desirable roller pressure interfaces being achieved between rolls of drafting roller pairs and also draft zones of minimum lengths.